In general, a compressor is a mechanical apparatus for compressing the air, refrigerant or other various operation gases and raising a pressure thereof, by receiving power from a power generation apparatus such as an electric motor or turbine. The compressor has been widely used for an electric home appliance such as a refrigerator and an air conditioner, or in the whole industry.
The compressors are roughly classified into a reciprocating compressor in which a compression space for sucking or discharging an operation gas is formed between a piston and a cylinder, and the piston is linearly reciprocated inside the cylinder, for compressing a refrigerant, a rotary compressor in which a compression space for sucking or discharging an operation gas is formed between an eccentrically-rotated roller and a cylinder, and the roller is eccentrically rotated along the inner wall of the cylinder, for compressing a refrigerant, and a scroll compressor in which a compression space for sucking or discharging an operation gas is formed between an orbiting scroll and a fixed scroll, and the orbiting scroll is rotated along the fixed scroll, for compressing a refrigerant.
While the reciprocating compressor has superior mechanical efficiency, such a reciprocating motion causes serious vibration and noise problems. Due to these problems, rotary compressors have been developed because of compact size and excellent vibration characteristics. A rotary compressor is constructed such that an electric motor and a compression mechanism part are mounted on a driving shaft. A roller located around an eccentric portion of the driving shaft is located within a cylinder defining a cylindrical compression space, at least one vane extends between the roller and the compression space to partition the compression space into a suction region and a compression region, and the roller is eccentrically located within the compression space. Generally, the vane is constructed to press a surface of the roller by being supported on a recessed portion of the cylinder by a spring. By means of such a vane, the compression space is partitioned into a suction region and a compression region as stated above. As the suction region becomes gradually larger along with the rotation of the driving shaft, a refrigerant or working fluid is sucked into the suction region. At the same time, as the compression region becomes gradually smaller, the refrigerant or working fluid therein is compressed.
In such a conventional rotary compressor, as the eccentric portion of the driving shaft rotates, the roller continuously comes into sliding contact with an inner surface of a stationary cylinder, and the roller continuously comes into contact with a tip surface of a stationary vane. Between the components which are thus in sliding contact, a high relative speed exists, and hence a friction loss occurs. This leads to a degradation of the efficiency of the compressor. Further, there is always the possibility of refrigerant leakage on a contact surface between the vane and the roller which are in sliding contact, thus reducing mechanical reliability.
Unlike the conventional rotary compressor which is targeted for a stationary cylinder, the U.S. Pat. No. 7,344,367 discloses a rotary compressor in which a compression space is located between a rotor and a roller rotatably mounted on a stationary shaft. In this patent, the stationary shaft longitudinally extends into a housing, and the motor includes a stator and a rotor. The rotor is rotatably mounted on the stationary shaft within the housing, and the roller is rotatably mounted on an eccentric portion which is integrally formed on the stationary shaft. Since a vane is engaged between the rotor and the roller so that the rotation of the rotor rotates the roller, a working fluid can be compressed within the compression space. However, in this patent, too, the stationary shaft and the inner surface of the roller are in sliding contact, and thus a high relative speed exists therebetween. Therefore, this patent still has the problem of the conventional rotary compressor.
International Laid-Open Publication (WO) No. 2008-004983 discloses a rotary compressor of another type, which comprises a cylinder, a rotor being eccentrically mounted relative to the cylinder on the inside of the cylinder, and a vane mounted in a slot in the rotor for sliding movement relative to the rotor, the vane being securely connected to the cylinder to force the cylinder to rotate with the rotor, thereby compressing a working fluid within the compression space formed between the cylinder and the rotor. In this publication, however, the rotor rotates by a driving force received from the driving shaft, so that it is necessary to install a separate electric motor part for driving the rotor. That is to say, the rotary compressor according to this publication is problematic in that the height of the compressor is inevitably large because a separate electric motor part has to be laminated in a height direction relative to a compression mechanism part including a rotor, a cylinder, and a vane, thereby making a compact design difficult.